JPH0230158B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lamp dimming device equipped with a safety device that detects lamp lighting abnormality and interrupts a power supply circuit to a lamp load.

Most copying machines are equipped with light control devices without abnormality detectors, but some exposure lamp light control devices are equipped with the following methods to detect abnormal lighting, etc. It had been taken.

(1) Method of directly detecting lamp load abnormalities (a) Install a temperature detector such as a temperature fuse or thermoswitch near the lamp load to detect the heat generated by the lamp load if it is lit for an abnormally long time. How to detect anomalies by detecting.

(b) A method in which a current transformer is installed in the power supply line of the lamp load, and abnormalities are detected by the length of time the current is generated.

(c) A method in which the light-emitting diode side of the photocoupler is connected to the power supply line of the lamp load, and an abnormality is detected based on the length of time that a detection current is generated from the phototransistor side.

(2) Method of indirectly detecting lamp load abnormalities A method of detecting abnormalities by measuring the drive time of the dimmer using a timer circuit, etc.

However, the above method (1)-(a) has problems with the mounting position of the temperature fuse, etc. (temperature detection position) and its response, and is not practical.
In method (b), a current transformer must be installed in addition to the feedback transformer installed in the lamp load for the dimmer, and there is a limit to the miniaturization of the lamp load area. In this method, since the withstand voltage of the photocoupler is low, resistors, diodes, etc. with relatively large capacitance are required, which is expensive.

In addition, particularly in the methods (1)-(b) and (1)-(c), a delay operation circuit or the like is required at the subsequent stage, which poses further problems in achieving miniaturization and cost reduction.

Since the above method (2) does not actually check for lamp load failures, it is inferior to the immediate detection method in terms of detection reliability.

Furthermore, even if one of the above methods is used to detect abnormal lamp lighting and interrupt the power supply circuit to the lamp load, if the lamp goes out due to the interruption, the abnormality will not be detected and the circuit will be cut off. There was also a problem in which the lamp would turn on again after it was released.

This invention was made in order to solve the above-mentioned problems, and it is possible to reliably detect abnormal lighting of a lamp load, facilitate miniaturization and cost reduction of the lamp load, and improve safety. The purpose is to obtain a high light control device.

In order to achieve the above object, the present invention controls a lamp load driving means by the output of a feedback circuit that generates a signal according to the driving voltage of the lamp load.
In the lamp dimmer device in which the lamp load is always lit at a predetermined light output, a series circuit of the lamp load drive means and a lamp load cutoff circuit that cuts off the power supply circuit of the lamp load during operation is connected to an alternating current circuit. Inserted in series in the power supply circuit,
AC impedance generating means is connected in parallel to the lamp load driving means, and the primary side of the transformer of the feedback circuit is connected in parallel to the series circuit of the lamp load and the lamp load cutoff circuit.

Further, there is an output generation circuit that generates an output when a signal is generated on the secondary side of the transformer, and an output generation circuit that operates when the output generation time of the output generation circuit exceeds a predetermined time to operate the lamp cutoff circuit. A safety device consisting of an abnormality detection circuit will be provided.

When the power supply circuit to the lamp load is cut off by the lamp cutoff circuit when the lamp load is turned on, the primary side AC impedance of the transformer and the AC generated by the AC impedance generating means are maintained until the power supply is disconnected. Due to the voltage division ratio of the impedance, the power supply voltage applied to the primary side of the transformer generates a signal on the secondary side of the transformer, so that the output generation circuit continues to generate an output, and the abnormality detection circuit cuts off the lamp load. This is to maintain the circuit in an operating state.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram of an exposure lamp dimming device for a copying machine to which the present invention is applied.

In the figure, 1 is a lamp load such as a halogen lamp, and an AC input circuit 2 is connected to a lamp load drive circuit 3 such as a phase control circuit using a triax.
AC voltage (current) is supplied through the lamp to light it.

4 is a feedback circuit that detects the drive voltage of the lamp load 1, converts it into DC, and supplies it to the comparator circuit 5; 6 is a DC input circuit to which DC voltage (current) D.C is input at a predetermined timing during copying; The output voltage supplied to the lamp load 1 can be set.

Reference numeral 7 denotes a soft start circuit, which prevents rush current in the lamp load 1 during the initial operation of the lamp dimmer, thereby extending the life of the filament of the lamp load 1, and miniaturizing the lamp load drive circuit 3. It is set up in

8 is an AC-DC conversion circuit, which rectifies and smoothes the AC voltage (power supply) A and C supplied to the AC input circuit 2 and converts it into a DC voltage (current).

Reference numeral 9 denotes a trigger circuit, which is supplied with DC voltage from the AC-DC conversion circuit 8, and receives the signal _S1 from the soft start circuit 7 or the comparison circuit 5 as the signal _S2 from the DC input circuit 6 and the signal from the feedback circuit 4. A trigger pulse is generated by changing _{the phase with respect to the AC input according to the control signal S 4 outputted} by comparing the signal S 3 with the AC input signal S 3 , and the conduction angle of the AC supplied to the lamp load drive circuit 3 is controlled to control the conduction angle of the AC input to the lamp load 1. Substantially controls the effective value of the supplied output voltage (current).

In addition, in the trigger circuit 9, the control signal S ₄ (voltage) is changed into a resistance value change using, for example, a photocoupler, and the time constant of a time constant circuit that determines the timing at which the trigger pulse is generated is changed, so that the generated trigger pulse is changed. Controls the phase for AC input.

10 is an output generation circuit that generates an output without substantially affecting the output when the feedback circuit 3 generates an output; 11 is an abnormality detection circuit; It is activated when the time period corresponding to the exposure cycle is exceeded, and abnormal lighting of the lamp load 1 is detected.

Reference numeral 12 denotes a lamp load cutoff circuit, which cuts off power supply to the lamp load 1 when the abnormality detection circuit 11 detects an abnormality and is activated. Reference numeral 13 denotes an abnormal state display circuit, which is provided to display and inform the operator when the abnormality detection circuit 11 detects a lighting abnormality in the lamp load 1.

14 is a DC level circuit, which converts the voltage into DC by the AC-DC conversion circuit 8 to the abnormality detection circuit 11.
and a circuit for converting and supplying a constant voltage level necessary for operating the abnormal state display circuit 13.

Next, the operation of the above-described embodiment configured in this manner will be explained.

First, a power switch (not shown) is turned on, and alternating currents A and C are input to the alternating current input circuit 2. and,
When the operator sets information such as the number of copies and turns on the copy start switch, the DC voltage D·C is input to the DC input circuit 6 at a predetermined timing.

On the other hand, since the trigger circuit 9 is supplied with the DC voltage from the AC-DC conversion circuit 8, it starts generating trigger pulses in response to the signal _S1 from the soft start circuit 7. This trigger path is the lamp load drive circuit 3.
The AC input circuit 2 controls the phase of the AC input from the AC input circuit 2 and supplies it to the lamp load 1.

Then, the lamp load 1 is turned on and exposure is started. Then, the feedback circuit 4 detects the drive voltage of the lamp load 1, converts it to direct current, and outputs a signal _S3 to the comparison circuit 5.

The comparator circuit 5 compares this signal _S3 with the voltage signal _S2 set by the DC input circuit 6, outputs a control signal _S4 , and activates the trigger circuit so that the lamp load 1 lights up with a predetermined light emission output. The phase of the trigger pulse generated at step 9 is changed.

Furthermore, when the feedback circuit 4 outputs a signal, the output generation circuit 10 generates an output in response. Then, the abnormality detection circuit 11 measures the time during which this output occurs, and is activated when the lamp load 1 does not turn off in a predetermined cycle for some reason, and the lamp load cutoff circuit 12 cuts off the power supply to the lamp load 1. The abnormal state display circuit 13 is operated to notify the operator of the lighting abnormality of the lamp load 1.

Next, a specific embodiment of the present invention will be described with reference to FIG. FIG. 2 shows only a portion related to the safety device in the embodiment shown in FIG. 1 as a specific circuit diagram.

In the figure, _Q1 is a bidirectional three-terminal thyristor (hereinafter referred to as a "TRIAT") of the lamp load drive circuit 3, and a trigger pulse from the trigger circuit 9 is applied to its gate G. This trial
The connection between the electrodes T ₁ and T ₂ of Q ₁ is to absorb the surge voltage generated by the lamp load 1 (inductive load) and to maintain the operating state even after the lamp load cutoff circuit 12 cuts off the power supply to the lamp load. A series circuit consisting of a resistor R ₁ and a capacitor C ₁ is connected in parallel, also serving as a circuit for holding .

T is a feedback transformer, whose primary side coil _L1 is connected in parallel to a series circuit of lamp load cutoff circuit 12 and lamp load 1, which will be described later, and whose secondary side coil _L2 is connected to a rectifier REC. ing. In addition, 1
The AC impedance ωL ₁ of the next coil L ₁ is made sufficiently larger than the AC impedance R ₁ +1/ωC ₁ of the resistor _R 1 and capacitor C ₁ described above.

A series circuit of a current limiting resistor R ₂ and a smoothing capacitor C ₂ is connected in parallel to the rectifier REC, and a resistor R ₃ is connected in parallel to the capacitor C ₂ . A voltage is output from this connection point a to the comparator circuit ₅ as a signal S3.

A feedback circuit 4 is constituted by the feedback transformer T, the rectifier REC, the resistors R ₂ , R ₃ and the capacitor C ₂ .

In the output generation circuit 10, D ₁ is a reverse input prevention diode, and a rectifier in the feedback circuit 4.
Depending on the REC output voltage (voltage at point b), the resistance
It is connected to charge the capacitor _C3 via _R4 . Note that this charging time constant R ₄ ·C ₃ is set to be extremely small.

Tr ₁ is an NPN type transistor, its base is connected via resistor R ₅ to point c, where the charging voltage of capacitor C ₃ appears, and its emitter is connected to the common line 15
The collectors are respectively connected to a constant voltage output point e of a DC level circuit 14, which will be described later, via resistors R ₆ and R ₇ .

Tr ₂ is a PNP type transistor, and its base is connected to the voltage dividing point d formed by resistors R ₇ and R ₆ , its emitter is connected to the constant voltage output point e, and its collector is connected to the common line 15 via resistor R ₈ . be.

In the abnormality detection circuit 11, a series circuit of a charging capacitor _C4 and a resistor _R9 is connected between a point f, which is an output terminal of the output generation circuit 10, and a common line 15. The charging time constants C ₄ and R ₉ are set to be slightly longer than the time corresponding to the exposure cycle of the copying machine so that the Zener diode ZD ₁ (described later) does not reach the Zener voltage during the exposure cycle.

A diode D ₂ is connected in parallel to the resistor R ₉ with its anode facing the common line 15.
When the lamp load 1 is lit normally, the exposure cycle is completed and the transistor TR ₂ is turned off, the capacitor C ₄ -> resistor R ₈ -> diode D ₂ loop allows the charge in the capacitor C ₄ to be discharged in a short time. It is set as.

ZD ₁ is a Zener diode, and its anode is connected to a connection point g between a capacitor C ₄ and a resistor R ₉ , and its cathode is connected to a point f through a parallel circuit of a resistor R ₁₀ and a capacitor C ₅ . The Zener voltage (breakdown voltage) of this Zener diode ZD ₁ is chosen to be less than the voltage generated across resistor R ₈ .
Capacitor _C5 is a capacitor for noise prevention.

Q ₂ is a programmable unification
It is a transistor (hereinafter abbreviated as "PUT"), whose gate G is connected to the h point on the cathode side of the Zener diode ZD ₁ , the anode A is connected to the f point, and the cathode K is connected to the common line 15 via the relay coil Ry. has been done. Furthermore, a diode _D3 for absorbing reverse voltage is connected in parallel to the relay coil Ry.

Then, the normally closed contact Ra ₁ of the relay coil Ry constituting the lamp load cutoff circuit 12 is inserted between the triax Q ₁ and the lamp load 1 as described above,
The normally open contact Ra ₂ of this relay coil Ry is inserted between the light emitting diode LD of the abnormal state display circuit 13 and its protective resistor R ₁₁ , the series circuit, and point f.

In addition, the output terminal of the AC-DC conversion circuit 8 and the common line 1
5, a resistor R ₁₂ and a Zener diode ZD ₂ constituting the DC level circuit 14 are connected in series, and output a constant voltage corresponding to the Zener voltage of the Zener diode ZD ₂ from point e.

Next, to explain the operation of this circuit, when a power switch and a copy start switch (not shown) are turned on and the copying machine enters an exposure cycle, a trigger pulse from the trigger circuit 9 triggers a try-on operation.
Q ₁ turns on at a given phase angle.

Thereby, the AC input supplied from the AC input circuit 2 is phase-controlled by the triax _Q1 , flows to the lamp load ₁ via the normally closed contact Ra1, and lights the lamp load 1.

When the lamp load 1 lights up, a voltage is generated across it, so the primary coil of the feedback transformer T
Voltage is also applied to L ₁ , and its secondary coil L ₂
A voltage is generated. This AC voltage is converted into a rectifier REC
The voltage is rectified by the resistors R ₂ and R ₃ , smoothed by the capacitor C ₂ , and output to the comparator circuit 5.
According to the procedure described above, the signal is processed so that the lamp load 1 is lit with a constant generated output.

Note that if the resistance of lamp load 1 is R ₀ , then R ₀ is very small and R ₀ ≪ωL ₁ holds, so
Its combined impedance is approximately R ₀ . on the other hand,
Since R ₀ < R ₁ +1/ωC ₁ holds true, when triac Q ₁ is turned off, resistor R ₁ and capacitor C ₁
The lamp load 1 will not be lit by the current bypassing the series circuit of , and no feedback voltage will be generated on the secondary side of the feedback transformer T.

Now, while lamp load 1 is lit, output generation circuit 1
0 capacitor C ₃ has a diode D ₁ and a resistor
Since the DC voltage rectified by the rectifier REC continues to be charged via _R4 , the potential at point c rises, and the transistor _Tr1 remains on.

When the transistor Tr ₁ is turned on, the DC current supplied from the AC-DC conversion circuit 8 whose voltage is regulated by the Zener diode ZD ₂ flows to the emitter of the transistor TR ₁ via the resistors R ₇ and R ₆ , so that the voltage at point d The potential drops and transistor Tr ₂ is also turned on.

These two transistors Tr ₁ and Tr ₂ remain on as long as there is a feedback output. Then, when the transistor Tr ₂ is turned on, the capacitor C ₄ of the abnormality detection circuit 11 starts to be charged with the charging time constant R ₆ ·C ₄ .

At the moment when the transistor Tr ₂ is turned on, the potential on the anode side of the Zener diode ZD ₁ is equal to the potential on the cathode side, but when the capacitor C ₄ starts to be charged, the potential on the anode side starts to decrease.

However, as mentioned above, the charging time constant
Since R ₉ and C ₄ are set to be slightly longer than the time corresponding to the exposure cycle of the copying machine, and the Zener diode ZD ₁ does not reach the Zener voltage during the exposure cycle, the lamp load 1 is turned on normally for a predetermined time. When the light is turned off, transistors Tr ₁ and Tr ₂ are turned off before the Zener diode ZD ₁ breaks down. Therefore, the charge stored in the capacitor _C4 is discharged in a short time through the loop of the resistor _R8 and the diode _D2 .

However, if for some reason the lamp load 1 remains lit even after completing the exposure cycle, the capacitor C ₄ is charged to the Zener voltage of the Zener diode ZD ₁ and the Zener diode ZD ₁ breaks down.

As a result, a breakdown current flows through the resistor _R10 , causing a voltage drop. Therefore, the potential at point h falls and the potential at the gate G of PUTQ ₂ becomes lower than the potential at the anode A, so PUTQ ₂ turns on and current flows through the relay coil Ry.

When current flows through relay coil Ry, its normally closed contact Ra ₁ (lamp load cutoff circuit 12) immediately opens to cut off the power supply to lamp load 1.
At the same time, the normally open contact Ra ₂ closes to supply power to the light emitting diode LD of the abnormal state display circuit 13 to cause it to emit light, thereby notifying the operator of the abnormality of the lamp load 1.

Note that after the Zener voltage applied to the Zener diode ZD ₁ breaks down, the gate potential of PUTQ ₂ is kept constant due to the voltage drop across the resistors R ₉ and R ₁₀ .

In addition, the normally closed contact Ra ₁ of the lamp load cutoff circuit 12
Even if the lamp load 1 is turned off by opening, the above-mentioned R ₁ +1/ωC ₁ ≪ωL ₁ holds true, so the resistance R ₁
Current flows through the primary coil L ₁ of the feedback transformer T through the series circuit of the capacitor C 1 and the capacitor C ₁ , and voltage continues to be generated on the secondary side.

Therefore, the transistors Tr ₁ and Tr ₂ are kept on, the power supply to PUTQ ₂ is not cut off, and current continues to flow through the relay coil Ry.
The open state of the normally closed contact Ra ₁ and the closed state of the normally open contact Ra ₂ are maintained.

This stabilizer is automatically reset by turning off the power switch (not shown) and opening the power supply, all power supply is cut off, PUTQ ₂ is turned off, and the charge in capacitor C ₄ is also discharged. Ru.

Incidentally, according to this embodiment, a disconnection of the lamp load can also be detected.

If lamp load 1 is disconnected, for example during an exposure cycle, R _{1 +}
1/ωC ₁ ≪ωL ₁ holds, so tryack Q ₁
Even if the is turned off, current flows to the primary coil _L1 of the feedback transformer T through the series circuit of the resistor _R1 and the capacitor _C1 , which are AC impedance generating means, and the current is 2 depending on the voltage division ratio of the AC impedance.
Voltage continues to be generated on the next side.

Therefore, as in the case described above, PUTQ ₂ of the abnormality detection circuit 11 is turned on and the relay coil is turned on.
energizes Ry, thereby abnormal state display circuit 1
The normally open contact Ra ₂ of No. 3 closes, and the light emitting diode LD emits light to notify you of an abnormality (in this case, a disconnection of the lamp load).

It goes without saying that even if the lamp load 1 is disconnected before the exposure cycle, it can be detected in the same way.

The embodiments in which the present invention is applied to an exposure lamp dimmer for a copying machine have been described above, but the present invention is not limited to this and can be similarly applied to dimmers for other various devices that light lamps. Of course. .

As described above, according to the present invention, the safety device monitors lighting abnormalities in the lamp load, and when a lighting abnormality occurs, it is immediately detected and the power supply circuit to the lamp load is cut off. After that, the cut-off state is maintained until the power is disconnected, so it is possible to quickly take measures against abnormal lighting of the lamp load, and there is also a risk of overheating due to continued abnormal lighting or repeated cut-off lighting. This can greatly improve the safety of the equipment.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an exposure lamp dimming device for a copying machine showing one embodiment of the present invention, and FIG.
FIG. 3 is a specific circuit diagram of a portion related to a safety device in the illustrated embodiment. 1...Lamp load, 2...AC input circuit, 3...
...Lamp load drive circuit, 4...Feedback circuit, 10...
...Output generation circuit, 11...Abnormality detection circuit, 12...
... Lamp load cutoff circuit, 13 ... Abnormal condition display circuit, Q ₁ ... Triack, R ₁ , C ₁ ... Series circuit of resistor and capacitor, T ... Feedback transformer,
Ry...Relay coil, Ra ₁ ...Normally closed contact, Ra ₂ ...
...Normally open contact, LD...Light emitting diode.

Claims (1)

[Scope of Claims] 1. A lamp regulator in which a lamp load driving means is controlled by an output of a feedback circuit that generates a signal according to a driving voltage of the lamp load, so that the lamp load is always lit at a predetermined light emission output. In the optical device, a series circuit including the lamp load driving means and a lamp load cutoff circuit that cuts off the power supply circuit of the lamp load during operation is inserted in series in an AC power supply circuit, and connected in parallel to the lamp load drive means. AC impedance generating means is connected, the primary side of the transformer of the feedback circuit is connected in parallel to the series circuit of the lamp load and the lamp load cutoff circuit, and a signal is generated on the secondary side of the transformer. and an abnormality detection circuit that operates when the output generation time of the output generation circuit exceeds a predetermined time to operate the lamp cutoff circuit. When the power supply circuit to the lamp load is cut off by the lamp cutoff circuit during lighting, the primary side AC impedance of the transformer and the AC impedance due to the AC impedance generating means are divided until the power supply is disconnected. A signal is generated on the secondary side of the transformer by the power supply voltage applied to the primary side of the transformer due to the voltage ratio, and as a result, the output generation circuit continues to generate an output, and the abnormality detection circuit interrupts the lamp load. A lamp dimmer equipped with a safety device that maintains a circuit in an operating state.